Slashdot videos: Now with more Slashdot!

View

Discuss

Share

We've improved Slashdot's video section; now you can view our video interviews, product close-ups and site visits with all the usual Slashdot options to comment, share, etc. No more walled garden! It's a work in progress -- we hope you'll check it out (Learn more about the recent updates).

Noble as in inert - it's not supposed to react to form a stable molecule.

Noble doesn't imply non-reactive, all of the noble elements can be ionized, with enough energy, just like any other element. What it means is they have a stable electron configuration. Helium, Neon, Argon, Krypton, Xenon, and Radon all have there outermost electron orbital shells filled. This means they're not inclined to give, borrow, or take electrons from other elements, this is why there called noble.

The fact that argon hydride was found in space implies that krypton, xenon, and radon hydride can also be found in space.

they're not inclined to give, borrow, or take electrons from other elements

Except these aren't the words used on the wiki [wikipedia.org] page. The word I was taught is "share". For example, Hydrogen has one electron and desires two for stability. So it shares one from Oxygen or Carbon, etc. And in that sharing, Oxygen (desiring two) gets its needs satisfied by sharing one each with two Hydrogens.

...you want to 1-up him you'll have to go for the quantum mechanic explanation of bonds. As far as *useful* models for chemical bonds go, even chemists use something pretty far from the "truth" . There are valence bond theory, orbital hybridization, resonance, and quite a few more.

When it comes to explaining nature, you use the model that is most USEFUL for what you want to explain, not for the most complicated one possible to impress your peers because you are so smart.:) That is why in many books atoms are still represented by red, white, blue "balls" and no one complains about it.

And by the way, the in the oxygen-hydrogen bond oxygen actually does sort of "borrow" the electron - the probability distribution for the location of that electron shifts towards the nucleus of the oxygen. That is why water molecules, while actually neutral (if not ionized), still act polar - the oxygen is essentially negative, the hydrogens positive. There is no equal "sharing".

...that electron shifts towards the nucleus of the oxygen. That is why water molecules, while actually neutral (if not ionized), still act polar - the oxygen is essentially negative, the hydrogens positive.
That is not why water acts polar. Water acts polar because of the nature of the oxygen atom itself. It has 6 electrons and wants to share 2 more. The electrons pair up into 4 groups or areas. Two of those areas are on the Oxygen a

My original reason for posting was to point out that no atom is "taking" anything.

When you've got "taking" of an electron, you've got ionisation.

Well, TFA states explicitly that it the argon36 is essentially sharing an electron with hydrogen.So it appears there might be some "sharing" even if there is no "taking". Very polite. Plays well with others.

> Water acts polar because of the nature of the oxygen atom> itself. It has 6 electrons and wants to share 2 more. The> electrons pair up into 4 groups or areas. Two of those areas are> on the Oxygen atom only...think of them as rabbit ears.

Sounds like what I studied in school; Only thing missing is that it is the geometry of putting 4 points around a central point that means you must get bunny ears and can't have a straight line (which would be non-polar)

Sort-of true. It's actually a consequence of the symmetries of p and s orbitals. Hybridising one s and three p orbitals (each oriented on one of the x, y and z axes gives you four "sp^3" orbitals. But that's true for any atom, not just oxygen. The symmetries involved - well can you think of a way that orients four directions in space in a maximally symmetrical manner and which doesn't end up with a tetrahedral orientation of the resultant orbi

Yes it did, originally. For the first 30 or 40 years after they were discovered, none of them had any known chemical compounds. Off the top of my head, xenon compounds were discovered in the late 1940s, krypton by the late 1950s, I'm not sure about argon's history, and neon compounds were announced some time since I was a student, so post 1980s.

all of the noble elements can be ionized, with enough energy, just like any other element. What it means is they have a stable elec

Noble In Name Only
I thought we could rely on these gasses to stay true to their column on the periodic table, but, no, they've sold out, just like that whorish oxygen and hydrogen, which will twerk with even the most sordid elements of society.
We're just going to have to look elsewhere for the stability we crave at all levels.

When I first learned about the elements many years ago, the description for those elements in the rightmost column was "inert". This means completely non-reactive.

Later on, when chemists made compounds of xenon, they realized the elements might not be so inert, after all. They gave the elements a new name: noble. They were not truly inert, but tended to have that tendency. Like other noble elements--such as gold or platinum--the elements in the rightmost column were disdainful of mixing with the hoi-polloi. It didn't mean they couldn't combine with other elements; they are just disinclined.

Actually, it's much more complicated. The gas Argon got its name from greek "argos", which means inert. The chemical group got the name of "noble gases" at the end of the 19th century from William Ramsay (Nobel prize in 1904). The first compound of a noble gas was discovered in 1962 by Neil Bartlett. Argon was the last noble gas for which a compound could be synthesized (2000).

That far right side of the Periodic Table...where Helium, Neon, Xenon, Argon, and Radon live. Those elements have always been taught as being chemically inert (i.e. not able to be combined with any other elements), hence why they are called "noble" gases. This apparently is the first instance where that rule isn't necessarily true.

This isn't even a compound, though. It's a molecular ion, ArH+. If you added an electron to it, it would fall apart, since ArH (neutral) is not bound.

A similar molecular ion exists for helium, HeH+. This ion is very important for the evolution of the early universe, since it can emit IR radiation to cool gas clouds, allowing stars to form from the nearly-pure H/He clouds that existed after the big bang.

You get a big ol WHOOSH today. That was a joke. JustOk called the show Big Bang but the show's name is The Big Bang Theory, hence why AC said it was just a theory. You are so eager to get your troll on, you miss some of the obvious stuff.

Noble elements aren't that because they CANNOT combine with things, they are that because they RARELY combine with things.Their outer shell is pretty bloated, so the amount of things they can combine with are extremely limited.

Title is so horribly wrong.A better title would have been "Less Noble, argon compound found in space."More so because it was found in nature, which is pretty damn impressive to find.

Several of the others form more-or-less stable molecules- usually with Hydrogen, none had been found for Argon up to now.The circumstances under which it forms appear to be rather extreme. I don't know enough (ok, anything) about Nuclear Chemistry to know if it is significant that the Isotope is Ar36 rather than the Ar40 we get here. Normally it would make no difference but this is an extreme case.

36Ar is the cosmically abundant isotope. On Earth, most argon is 40 Ar, because it comes from the radioactive decay of 40K. Earth is poor in 36Ar because it formed at a position in the solar nebula too warm to condense Ar.

Argon compounds have been formed in the lab for nearly 15 years. No Nobel compounds have been directly observed in space of any kind, which is the new part, not that Argon in particular was found in a compound.

That far right side of the Periodic Table...where Helium, Neon, Xenon, Argon, and Radon live. Those elements have always been taught as being chemically inert (i.e. not able to be combined with any other elements), hence why they are called "noble" gases. This apparently is the first instance where that rule isn't necessarily true.

Of course it took the energy of the collapse of a star to produce those compounds, so for practical purpose, those gases are still all pretty noble.

But worth explaining for others that either didn't have chemistry class or maybe snoozed through it. The atoms of "noble" gases have their outer electron shell full so are very non-reactive, they usually don't make chemical bounds with other elements except under extraordinary circumstances requiring a lot of energy. Helium, neon, argon, and radon are probably the ones most people have heard mentioned at some time in daily life.

Argon forms compounds without too much coercion. Back in the mid '60s chemists were playing with them regularly. As I understand it (I'm NOT a chemist and haven't done this myself):

Just mix argon and fuourine in a pressure vessel and heat it up. (VERY CAREFULLY! Fluorine gas is deadly!) You'll quickly get copious amounts of argon difluoride, tetrafluoride, and even some hexafluoride. These are stable enough to stick around once you bring things down to room temperatures.

Did a little checking. It's Xenon that they were playing with back then. Xenon is reasonably easy to convince to make covalent bonds, and some of its compounds are used industrially and available in commercial quantities.

Argon is less reactive, and they didn't get it to form compounds until 2000, with some encouragement from an ultraviolet light source to kick an electron up to another level.

I'm going to call BS. You thought it was Argon, were wrong, got called out, and now you're trying to backtrack. Your argument was that the article's title was wrong because Argon was shown to be non-noble years ago and that you could buy compounds now. Unless you for some reason think that the existence of Xenon difluoride implicates the existance of argon compounds.

I should probably stop you there. I'm a professional chemist.

You can claim I was trying to backtrack, or you can accept that I typed the wrong element because the entire story is about Argon. I personally know a guy who studies argon complexes spectroscopically and he's been doing it for a lot longer than the date of this article.

I am well versed in group 18, and use one of its members (Argon!) pretty much every day (except weekends).

Chemists have known for a long time that the "noble" gasses aren't really

This. Instead of shopping for Christmas before the Baptists get out of church and flood the stores, I am looking up noble gases, then noble metals, and then electric potential on a Sunday morning.... sigh.

Do we categorize Argon as a non-noble gas, or do we redefine what a noble gas actually is?

We don't necessarily need to do either; the article headline is a little bit misleading.

Non-reactivity, or the non-existence of molecules is not inherent to the definition of Noble gas.
Non-reactivity is a description of what is believed to be true about noble gasses.
The noble gasses were long believed to be completely nonreactive; but now, compounds of Xenon, Krypton, Radon....
and now Argon are known. We

These things are often oversimplified to teach the basics. For the purposes of a introductory chemistry class, the group 18 elements are not going to play a part in chemical reactions under everyday circumstances. This is simplified down to 8 valence electrons. When one talks about s^2p^6 for everything but He, all the eyes starts going into the forehead and all the other details become lost and questions such as 'is this going to be on the test' get most of the attention. What we are talking about here is not ordinary chemistry, but supernovas, which build most other elements out of the noble gas Helium.

not going to play a part in chemical reactions under everyday circumstances.

The funny thing, is after some very difficult attempts it took to form the first xenon compounds, confirming it is very difficult to form such compounds, someone realized it could be done a lot easier with just UV light from the sun. Filling a jar with fluorine and xenon gas, leave it in the sun, and you will get xenon fluoride.

Do we categorize Argon as a non-noble gas, or do we redefine what a noble gas actually is?

Neither.

A noble element is one that has its valence shell full. That's it. That's why it's in that column of the periodic table.

It doesn't mean it won't react, it's just got less reason to (atoms normally bond to fill up their valence shell with electrons by sharing them with other atoms). That just means that two noble elements are not likely to bond together (no sharing going on). However, that doesn't mean some othe

I got a shock 50 years ago, when I read an article about xenon compounds when I was 13. My background reading had given me the impression that the 'noble' elements did not form compounds.

Note, once (same school year) I was meant to have read a chapter on Calcium for Chemistry homework, which I didn't read - but my background reading was sufficient, so that everybody implicitly assumed that I had read that chapter very well!

I was quite some time behind you, but the libraries I was borrowing from were even further behind. I learned about the nobles from one of Asimov's excellent non-fiction popular chemistry books, and from a 1950s edition of Britannica. I was thrilled when I found out that compounds actually existed.

Anything will combine with anything -- it just won't stay combined. You can rip as many electrons off (say) neon as you like, throw it in with another species, and watch them stick together long enough for neon to nab the electrons it wants -- but you won't get a compound that persists. Similarly, you can force xenon and anything together, but only a few pairings will produce compounds stable at even cryogenic temperatures.

- a noble gas has been found in space (this confirmed people's expectations that argon-36 could be found as part of a supernova, even though argon-40 is much more common on Earth - note that argon-36 is also available on Earth, just in smaller quantities, it's not a new isotope)- a noble gas molecule has been found in space (previously, argon compounds were only detected following Earth-based lab experiments)

The significant part of this discovery is not:

- that a noble gas can form a compound. Argon has had known compounds since 2003. Xenon has had known compounds since 1962, some of which are even stable at normal room temperature/pressure.